1mhz
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METHANE MONOOXYGENASE HYDROXYLASE
OverviewOverview
Methane monooxygenase (MMO), found in aerobic methanotrophic bacteria, catalyzes the O2-dependent conversion of methane to methanol. The soluble, form of the enzyme (sMMO) consists of three components: a reductase, a, regulatory "B" component (MMOB), and a hydroxylase component (MMOH), which, contains a hydroxo-bridged dinuclear iron cluster. Two genera of, methanotrophs, termed Type X and Type II, which differ markedly in, cellular and metabolic characteristics, are known to produce the sMMO. The, structure of MMOH from the Type X methanotroph Methylococcus capsulatus, Bath (MMO Bath) has been reported recently. Two different structures were, found for the essential diiron cluster, depending upon the temperature at, which the diffraction data were collected. In order to extend the, structural studies to the Type II methanotrophs and to determine whether, one of the two known MMOH structures is generally applicable to the MMOH, family, we have determined the crystal structure of the MMOH from Type II, Methylosinus trichosporium OB3b (MMO OB3b) in two crystal forms to 2.0 A, resolution, respectively, both determined at 18 degrees C. The crystal, forms differ in that MMOB was present during crystallization of the second, form. Both crystal forms, however, yielded very similar results for the, structure of the MMOH. Most of the major structural features of the MMOH, Bath were also maintained with high fidelity. The two irons of the active, site cluster of MMOH OB3b are bridged by two OH (or one OH and one H2O), as well as both carboxylate oxygens of Glu alpha 144. This, bis-mu-hydroxo-bridged "diamond core" structure, with a short Fe-Fe, distance of 2.99 A, is unique for the resting state of proteins containing, analogous diiron clusters, and is very similar to the structure reported, for the cluster from flash frozen (-160 degrees C) crystals of MMOH Bath, suggesting a common active site structure for the soluble MMOHs. The, high-resolution structure of MMOH OB3b indicates 26 consecutive amino acid, sequence differences in the beta chain when compared to the previously, reported sequence inferred from the cloned gene. Fifteen additional, sequence differences distributed randomly over the three chains were also, observed, including D alpha 209E, a ligand of one of the irons.
About this StructureAbout this Structure
1MHZ is a Protein complex structure of sequences from Methylosinus trichosporium with FE as ligand. Active as Methane monooxygenase, with EC number 1.14.13.25 Known structural/functional Site: . Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of the hydroxylase component of methane monooxygenase from Methylosinus trichosporium OB3b., Elango N, Radhakrishnan R, Froland WA, Wallar BJ, Earhart CA, Lipscomb JD, Ohlendorf DH, Protein Sci. 1997 Mar;6(3):556-68. PMID:9070438
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